A submerged or submarine pipeline is a pipeline passing under water, which is typically laid on the seabed, or inside a trench below the seabed. The pipeline may also be partially located on-land. Submarine pipelines are used primarily to carry oil or gas but may also be used to transport other materials.
Submerged pipelines are often wrapped with insulating materials. Insulating materials provide many benefits. For example, insulating materials may provide flow assurance by maintaining flow rates. This, in turn, optimizes productivity and lowers processing costs. Also, insulating subsea equipment and piping reduces the costs of cooling reservoir fluids and helps maintain temperatures so that waxes and hydrates do not form, thereby minimizing the risk of diminished flow rates and blockages.
Despite various prevention efforts, pipelines are susceptible to corrosion, which causes costly damage every year. As a result of this corrosion, pipeline sections often have to be taken out of service and replaced. In order to identify pipeline areas or sections in need of repair or replacement, inspection of the pipelines is generally required. Detection of areas of corrosion can allow for corrective actions prior to a potentially catastrophic event. Various techniques may be employed to detect corrosion in pipelines.
Inspection of submerged pipelines, including pipelines at depths of 4,000 meters, poses additional difficulties over inspections of pipeline above water or in relatively shallow water. Certain inspection techniques, such as infrared inspections, require direct contact with the pipeline. To utilize such techniques on submerged pipelines, any insulating material as well as any other marine build up on the pipes must be removed before testing. Preparation for testing can be very expensive. Other techniques provide for external inspection of pipelines without removing the insulating material and/or marine buildup. For example, pulsed eddy current (PEC) sensors, such as the Applus RTD® INCOTEST, may be utilized to survey ferrous pipes and vessels through thermal insulation, protective coatings and marine buildup. PEC sensors are typically deployed as a single sensor by a diver or remotely operated vehicle (ROV). Manipulation of the sensor along pipelines, particularly deeply submerged pipelines, can be difficult, time-consuming, and inefficient.
Accordingly, a need exists for improved apparatuses and methods to more efficiently inspect submerged surfaces, including submerged pipelines.